The Childhood Development after Cochlear Implantation (CDaCI) Study is a multisite, prospective investigation of a large and diverse cohort of US children with cochlear implants. Our primary objective is to evaluate the effect of variables that influence language learning after implantation. Success in spoken language is seen to flow from success in other spheres of development. Thus our aims are driven by hypotheses that relate variability in post-implant spoken language outcome to environmental, social, interventional, and biological influences. A major challenge in early childhood research relates to the reliable sampling of language and other communicative behaviors. We address this challenge with hierarchical measures and videoanalytic techniques that allow us to track communicative skills as they emerge. We will build on this research experience to examine how spoken language skills unfold in children participating in the study, evaluating their: 1 .oral language and literacy skills, 2.speech production, S.speech recognition, 4.cognitive skills, S.social interaction & behavior, 6.relationships with family members, and T.health-related quality of life. CDaCI Study participants consist of (Cl)children who received a cochlear implant before the age of 5 years (n=188) and a control group (n=97) of normal hearing (NH) age-mates. Average ages at enrollment were 2.2 years (Cl)and 2.3 years (NH).So, as CDaCI participants began the study as toddlers and preschoolers, they will now embark on their early elementary school experience. Despite wide recognition of the benefits of early cochlear implantation, there remains uncertainty with respect to clinical, rehabilitative, and educational strategies that enable cochlear implant technology to be used to its greatest potential for oral language acquisition. Modifiers of linguistic outcome become even more compelling as Cl children face the performance and social demands of their early elementary school years. As we gather additional longitudinal data, we will apply statistical processes to fully evaluate growth trajectories and indices of performance across domains. A prospective, multidimensional study of Cl with concurrent NH controls, as well as population-based control group (NICHD), offers prospectsfor novel, generalizable insights into the sources of variation in oral language learning after cochlear implantation in childhood.